The present invention relates to the separation of liquid and solid particles from a gas and more particularly to an improved spray booth for removing paint overspray from air.
Water-wash spray booths are well known in the art and generally comprise a water curtain flowing over a so-called floodsheet against which overspray from one or more spray guns is directed. The overspray mingles with the water flowing over the floodsheet and is collected in a reservoir. Many spray booths rely on a pump for the supply of water to the water curtain, although recently many "pumpless" booths have become known in the art. These booths rely on a very high velocity exhaust air stream to pick up water from the reservoir and to mingle it with the overspray. The entrained water is separated from the exhaust air prior to discharge of the cleansed air by the exhaust fan. The separated water is used to maintain the floodsheet. Early booths of this type require considerable maintenance since the paint laden water is continuously recirculated through the system and also because there is a tendency for the paint to float as a foam on the surface in the reservoir.
In an improved water-wash spray booth, as described in Kearney U.S. Pat. No. 4,096,966, water flows from the floodsheet into a main reservoir or holding tank. An opened top cone or chamber, sometimes referred to as a Dehon cone, is positioned immediately below the surface level within the reservoir. A pump continuously draws liquid from the reservoir and causes a high velocity stream of such liquid to flow through a venturi and back into the reservoir. Through this arrangement, both foamed paint particles floating on the surface of the reservoir and paint particles suspended within the liquid are drawn into the chamber and forced through the venturi back into the reservoir. This device breaks up the paint particles into very small particles which more easily separate solvent from paint solids so that the solids can eventually settle as a dense mat on the bottom of the reservoir. This system has greatly reduced the volume of paint waste disposal from the spray booth and also has reduced maintenance on the spray booth. However, periodic maintenance still is required on the pump which circulates liquid from the reservoir through the Dehon cone or chamber and through the venturi back to the reservoir.